To improve the quality of images obtained by image-forming devices, two-layer or three-layer intermediate transfer belts including a rubber-elastic layer formed of a rubber-elastic resin, etc., have been suggested (for example, see Patent Literature 1).
Since such an intermediate transfer belt having a rubber-elastic layer has excellent flexibility, a stable transfer image area can be formed on the intermediate transfer belt by the uniform contact between the belt and a photo conductor, etc., and stress applied to toner between the belt and the photo conductor, etc., can be reduced. Therefore, by using an intermediate transfer belt including a rubber-elastic layer, missing defects on line image can be prevented, and fine line printing definition can be improved. Further, it is also known that when paper having a rough surface (rough paper) is used, the tracking ability over uneven paper is improved, which prevents a reduction in image quality.
In such a high-quality image-forming intermediate transfer belt, a rubber-elastic property is provided in the belt thickness direction, and the toner releasability that is necessary for the transfer belt is required as an important factor. Namely, to transfer toner from the surface of the intermediate transfer belt to a medium such as paper, toner releasability is required. Therefore, it is not desirable for a rubber-elastic layer having toner adhesiveness to be exposed to the surface of the intermediate transfer belt; accordingly, a resin surface layer having a low friction coefficient and excellent toner releasability is generally formed on the rubber-elastic layer (see, for example, FIG. 1). It is known that making such a surface layer as thin as possible is useful for obtaining high image quality, and various intermediate transfer belts having a thin surface layer have been suggested.
However, since the intermediate transfer belt for an image-forming device receives external force from paper and a sliding member such as cleaning blade, roller, that is in contact with a belt surface when the surface layer has a thin film, stress applied to the belt is concentrated on the thin film surface layer, which causes problems such as cracking or peeling of the surface layer. Moreover, even when the hardness of the entire belt is increased to overcome such a problem, although excellent durability can be attained, there is a problem of reducing the image quality.
Thus, it is extremely difficult for an intermediate transfer belt having a thin surface layer to attain high external friction resistance, etc., while maintaining high image quality.